The embodiment relates to a projection display apparatus that modulates light incident on display elements according to an image signal, and emits the modulated light to project on a screen so as to display an image. In particular, the embodiment relates to a projection display apparatus capable of preventing deterioration of a polarization converting element caused by heat.
Projection display apparatuses using liquid crystal display elements that modulate and emit incident light are in widespread use. In recent projection display apparatuses, polarized light is incident on liquid crystal display elements. Therefore, indefinite polarized light emitted from a light source is conformed to either first polarized light or second polarized light by a polarization converting element, so as to increase light use efficiency.
The polarization converting element is provided with a polarizing beam splitter (PBS) prism that splits the incident indefinite polarized light into first polarized light and second polarized light perpendicular to each other, and is provided with half-wave plates that convert the first polarized light into the second polarized light, or the second polarized light into the first polarized light.
The polarization converting element is likely to be heated since light flux emitted from the light source is collected thereon. The PBS prism and the half-wave plates are bonded together by use of an adhesive, and the PBS prism itself is formed of plural prisms that are also bonded to each other by the adhesive . Once the polarization converting element is heated due to the collected light flux, the adhesive is degraded through an oxidation process and a photochemical reaction process.
When the half-wave plates are made of polycarbonate which is an organic material, the plates are easily deteriorated since polycarbonate is relatively sensitive to heat. Thus, the polarization converting element is generally cooled by a cooling fan.